JPS623417A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the lubricity and electromagnetic transducing characteristic of the titled medium by providing minute protrusions having heights in a speci fied range and in limited number per unit area on the surface of a ferromagnetic metallic thin film furnished on a nonmagnetic carrier and forming a plasma- polymerized film thereon. CONSTITUTION:The minute protrusion 3 is provided on the surface of the ferro magnetic metallic thin film 2 furnished on the nonmagnetic carrier 1. The plasma-polymerized film 4 is further provided on the ferromagnetic metallic thin film 2. The height of the fine protrusion 3 is preferably regulated to 50-400Angstrom and the number of minute protrusions per unit area is preferably controlled to 1X10<7>-8X10<7> unit/mm<2>. Moreover, the two-dimensional size (d) of the minute protrusion is favorably adjusted to 500-2,000Angstrom . Iron, cobalt, nickel and other ferromagnetic metals or a ferromagnetic alloy of Fe-Co, Fe-Ni, etc., are used as the ferromagnetic metallic thin film. The plasma-polymerized film is formed by polymerizing an org. gaseous monomer in plasma resulting from electric discharge induced by DC, AC, high frequency, microwave, etc., on the ferromagnetic metallic thin film. The lubricity and electromagnetic charac teristic are thus improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium comprising a ferromagnetic metal thin film as a magnetic recording layer on a non-magnetic substrate and a plasma polymerized film thereon. This invention relates to a magnetic recording medium with excellent electromagnetic conversion characteristics.

[Prior art]

Conventionally, as a magnetic recording medium, r-
γ-Fe2O3, Fe doped with pe 203, co
3O4, Co-doped Fe3O4, r-Fe 20
3 and Fe50. Powdered magnetic materials such as Bertolide compound, CrO2, etc. breakable powder or ferromagnetic alloy powder are dispersed in organic binders such as vinyl chloride-vinyl acetate copolymer, ζ styrene-butadiene copolymer, epoxy resin, polyurethane resin, etc. Coating type products have been widely used, in which a predetermined amount is applied and dried. In recent years, with the increasing demand for high-density recording, paper deposition methods such as vacuum evaporation, sputtering, ion blating, etc.
So-called metal thin film magnetic recording media, which do not use a binder and use a ferromagnetic metal thin film formed by plating methods such as atmospheric plating or electroless plating as a magnetic recording layer, are attracting attention, and various efforts are being made to put them into practical use. It is being done.

Conventional coating-type magnetic recording media mainly use metal oxides, which have lower saturation magnetization than ferromagnetic metals, as magnetic materials, so the thinning required for high-density recording leads to a reduction in signal output, which has reached its limit. Moreover, the manufacturing process is complicated, and it has the drawback of requiring large auxiliary equipment for solvent recovery and pollution prevention. In metal thin film magnetic recording media, a ferromagnetic metal with a higher saturation magnetization than the above-mentioned oxides is formed as a thin film without containing a nonmagnetic substance such as a binder. Moreover, the manufacturing process is simple.

As one of the conditions required for magnetic recording media for high-density recording, high coercive force and thinness have been proposed both theoretically and experimentally, and coating-type magnetic recording media are also required. There are great expectations for metal thin film magnetic recording media, which can be easily made thinner by an order of magnitude and have a high saturation magnetic flux density.

Furthermore, major problems concerning magnetic recording media made of ferromagnetic metal thin films include strength against corrosion and abrasion, and running stability. During the process of recording, reproducing, and erasing magnetic signals, the magnetic recording medium is subjected to high-speed relative motion with the magnetic head, but at this time, the movement must be smooth and stable, and at the same time, contact with the head must be maintained. There shall be no wear or damage due to

In order to improve the above problem, it has been proposed to provide a plasma polymerized film as a protective layer on a ferromagnetic metal thin film.
Same as J'! Tar1r4At, Hiro/No., same? -/j hiro 6≠3 issue, same 19-/601 issue, same j? -1710
No. 21, same! Tar/7/.

No. 2, No. 60-λ27JO, No. 1.0-J! ! 30
No., t 0-3j j J No. 7, 40-3172
No. 7, No. 4O-31721r, No. 40-! 7j33, 60-17136, 6O-J-7!37, 40-637λ, AO-J9rJj, 6O-
62t-26, etc. However, conventional metal thin film magnetic recording media with a plasma polymerized film as a protective layer have insufficient lubricity, especially in repeated friction, and in order to improve the repeated friction characteristics, the thickness of the plasma polymerized film must be increased. However, in this case, there is a problem that the electromagnetic conversion characteristics deteriorate and the characteristics of the metal thin film magnetic recording medium cannot be utilized, and an improvement has been strongly desired.

[Purpose of the invention]

An object of the present invention is to provide a magnetic recording medium that has improved the above-mentioned drawbacks, that is, a magnetic recording medium that has excellent lubricity, particularly excellent repeated friction characteristics, and excellent electromagnetic conversion characteristics.

[Structure of the invention]

The present invention provides a magnetic recording medium having a ferromagnetic metal thin film as a magnetic layer on a nonmagnetic support, and further provided with a plasma polymerized film thereon.
10 million to rooo million protrusions from 0 to ≠00^/stain 2
The present invention relates to a magnetic recording medium characterized in that it exists.

As a result of intensive research into improving the lubricity of metal thin film magnetic recording media provided with a plasma polymerized protective film, the present inventors found that
By providing a plasma polymerized film on the surface of the ferromagnetic metal thin film provided with the above-mentioned microprotrusions, fr
The present invention has been achieved based on the discovery that 4 lubricity is improved.

FIG. 1 shows the structure of a magnetic recording medium according to the present invention. The magnetic recording medium according to the present invention has minute protrusions 3 on the surface of a ferromagnetic metal thin film λ provided on a suitable support l. Further, a plasma polymerized film≠ is provided on the ferromagnetic metal thin film. Methods for forming microprotrusions 3 on the ferromagnetic thin film λ include coating, vapor deposition, sputtering, plating, ionization, and coating, vapor deposition, sputtering, plating, and ionization of fine particles, fine particulate matter, or island-like structures of metal alloys, metal oxides, organic substances, etc. onto a support. It is formed by a plating method, or a combination of these methods with etching, reverse snotter 1 reverse plating, etc., and then a ferromagnetic metal thin film is formed thereon by a method such as plating, vapor deposition, or sputtering. There is a method to obtain microprotrusions. Furthermore, when forming the ferromagnetic metal thin film itself, it is possible to obtain microprotrusions directly by selecting formation conditions, or by selectively etching with an ion beam after forming the ferromagnetic metal thin film. In the present invention, as a result of various studies, the dimensions of the microprotrusions are preferably 10 to ≠00^, and the number p ((In/-2) of microprotrusions per unit area is /0 million to rooo million). /n2 is preferred.

Furthermore, the two-dimensional size of the microprotrusion is a)! 00～koo
oo^ is preferable.

The ferromagnetic metal thin film in the present invention may be made of iron, cobalt, nickel or other ferromagnetic metals, or Fe-Co5
pe-Nis Co-Ni, Fe-C□ -Ni,
Fe-Rh, Co-P, Co-BXCo-Cu.

Co-Zn, Co-Y, Co-La, Co-Ce, C.

PrXCo Gd, Co-8m, Co-Pi, Co-
MnXFe-Gd, Fe-Tb, Fe-Cr, Co-
c, Ni-Cr, l;'e-co-Cr, Ni Co
Cr.

Fe-N1-CrXpe-co-Nic,co
NiNdXCo NiCe, co-Ni-ZnX
c, -Ni cu, co-Ni-wXCo Ni
A ferromagnetic alloy such as Re is formed into a thin film by electroplating, electroless plating, paper deposition method, etc. The film thickness is in the range of 0.02 to λμm when used as a magnetic recording medium. Yes, especially 0.0! ~
0. Reference μ-specialized range is preferable. The above ferromagnetic metal thin film also contains 0% Nz C% Ga) As) Sr, Zr, Nb
, Mo, Sn, Sb, Te, 0ssIr% Au, A
g, PbXB1, etc. may be contained. Paper deposition method refers to a method in which a substance is turned into vapor or ionized vapor in a gas or vacuum space and is deposited on a substrate, and includes vacuum evaporation method, sputtering method, ion plating method, and ion beam deposition method. , chemical vapor phase plating, etc.

Non-magnetic supports used in the present invention include plastic bases such as polyethylene terephthalate, polyimide, polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate, and polyphenylene sulfide, or AJ, Ti, and alloys thereof; Stainless steel etc.

The plasma polymerized film in the present invention refers to a film of an organic polymer material formed by polymerizing an organic monomer gas on a ferromagnetic metal thin film in plasma caused by discharge induced by DC, AC, high frequency, microwave, or the like.

At this time, the organic monomer gas may be directly ionized, or an organic monomer gas such as Ars He% 02, N2, N2, etc. may be introduced during gas discharge.

The pressure during plasma polymerization is preferably 10 Torr. The thickness of the plasma polymerized film in the present invention is preferably in the range of 20 to 300 mm, particularly preferably 20 mm. Organic monomer gases include tetrafluoromethane, tetrafluoroethylene, hexafluoroethane, and
Ropropane, octafluorocyclobutane, methane, ethylene, propylene, styrene, vinyl chloride, styrene, chlorobenzene, dimethylsiloxane, hexamethyldisilazane, diethylaminotrimethyl 7rane, etc. are used alone or in combination.

Further, in the present invention, the ferromagnetic metal thin film may have a single layer or a multilayer structure of two or more layers.

When ferromagnetic thin films are laminated, a nonmagnetic layer may be interposed between them. Preferred as the non-magnetic intermediate layer is cr.
XS i, ACMn, Bi,'ri.

This layer is made of 5nXPb, In, ZnXCu, or their oxides or nitrides. Further, the nonmagnetic layer may be provided on the substrate as an underlayer of a ferromagnetic thin film.

A magnetic film may be provided on both sides of the non-magnetic support, or a so-called pack layer may be provided on the back side of the non-magnetic support.

〔Example〕

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example L? A liquid containing calcium carbonate fine particles of various sizes dispersed in the following binder composition was applied to the surface of a polyethylene terephthalate film with a thickness of jμm.

Methyl ethyl ketone was used as the solvent, and coating was performed at various dilutions to vary the coating density of the calcium carbonate powder. On the undercoat film obtained in this manner, a CoNi ferromagnetic thin film of CN10 was formed by an oblique vapor deposition method using a continuous vapor deposition machine to a film thickness of /100^ to prepare several kinds of magnetic tape original fabrics. Microscopic protrusions are formed on the surface of the ferromagnetic metal thin film of the obtained magnetic tape, and their height h) is approximately equal to the protruding height of the calcium carbonate fine particles protruding from the lower m9 layer, and their two-dimensional dimension is (a) is an abbreviation of the λ-dimensional dimension of calcium carbonate fine particles protruding from the undercoat υ layer.

Try becoming twice as big. Next, using a continuous plasma polymerization apparatus, a plasma polymerized film was provided on the CoNi ferromagnetic thin film so as to have a film thickness of 000 g to produce a magnetic recording medium. To form a plasma polymerized film, pressurize a 1:1 mixed gas of methane, tet, and 770 romethane! xlO Torr
Plasma polymerization was performed using oW high frequency discharge.

The surface of the magnetic recording medium thus obtained has a height h),
Microprotrusions with the same density (p) as the magnetic film surface were maintained.

Comparative Example In Example 1, a ferromagnetic metal thin film was directly formed on a polyethylene terephthalate film without providing an undercoat layer, and a plasma polymerized film was formed to a thickness of 2 without providing microprotrusions on the surface.
00 big! A sample of 00^ was prepared.

The thus obtained Kuhara fabric is rwx. A widthwise slit was made and the repeated friction characteristics and electromagnetic conversion characteristics were measured using the following method.

l, Repeated friction characteristics SUS 4! Traveling speed 1 for λOJ stainless steel rod
The friction coefficient μ was investigated during the first run at 4AWm/3ec and after running 2QQ times.

2. Electromagnetic conversion characteristics ImVTR (FUJIX-rm7 manufactured by Fuji Photo Film)
) was used to measure the playback output signal of the jMHz video signal after one run and after 200 runs.

The results were as shown in Table 7 and λ.

In this way, the height is to-4too^, the density is 10 million to r
A magnetic recording medium having a plasma-polymerized film of methane and tetrafluoromethane mixed gas on a CoNi vapor-deposited magnetic film with minute protrusions of 2 mm/thin size has excellent resistance to repeated friction and excellent video signal reproduction output characteristics. It is something.

Example 2 A liquid in which silicon oxide fine particles of various sizes were dispersed in the same binder composition as in Example 1 was applied onto a polyimide film with a thickness of 12 μm. Methyl ethyl keto/ was used as the solvent, and coating was carried out at various dilutions in order to change the coating density of the silicon oxide powder. CoCr alloy (C:7
A ferromagnetic thin film having a film thickness of 10% by weight/100^ was formed to prepare various magnetic tape materials. Next, using a continuous plasma polymerization device, the film thickness /
A magnetic recording medium was fabricated by forming a plasma polymerized film so that the magnetic flux was 50^. The plasma polymerized film was formed by plasma polymerizing styrene under the same conditions as in Example 1. Example! The lubricity under repeated friction and the electromagnetic conversion ratio were measured using RFIJ, and the results were as shown in Table 3.

Like this height! O~4tool, density 10 million~r
CoCr vapor deposited fi with oooo million pieces/2 microprotrusions
A magnetic recording medium formed by forming a plasma-polymerized styrene film on the surface of an i-based film has excellent repeated friction lubricity and excellent video signal reproduction output characteristics.

〔Effect of the invention〕

The magnetic recording medium of the present invention has excellent lubricity in repeated friction and electromagnetic conversion characteristics, and provides a metal thin film type magnetic recording medium that is improved over conventional magnetic recording media.

[Brief explanation of the drawing]

FIG. 1 shows the basic structure of a magnetic recording medium according to the present invention. /...Support...Ferromagnetic metal thin film 3...Minute protrusions≠...Plasma polymerized film Patent claimant Fuji Photo Film Co., Ltd. Figure 1

Claims (1)

[Claims] In a magnetic recording medium comprising a ferromagnetic metal thin film on a non-magnetic support and a plasma polymerized film thereon, 1,000 protrusions with a height of 50 to 400 Å are formed on the surface of the ferromagnetic metal thin film.
A magnetic recording medium characterized in that there are 10,000 to 80 million pieces/mm^2.